(1) Field of the Invention
The present invention relates optical switches applicable to various devices for optical communication. In particular the invention relates to optical switches of the spatially optical coupled type using a plurality of tilt mirrors each of which has a reflective surface with an angle thereof being controllable.
(2) Related Art
For example, as conventional optical switches applied to various optical communication devices such as optical cross-connection devices, constructions which mechanically switch an optical fiber, or which use a waveguide device are generally known. However, conventional optical switches of this construction are limited to a scale of only tens of channels, and to realize large scale optical switches extending to thousands of channels as required for recent years, it is necessary to introduce new technology.
As one technology for realizing large-scale optical switches, the development of optical switches of the spatially optical coupled type which use micro-tilt mirror arrays manufactured for example by applying the technology for micro machining (MEMS: Micro Electric Mechanical System), is progressing. More specifically, there are the optical switches known for example by an article by D. T. Neilson et al., xe2x80x9cFully provisioned 112xc3x97112 micro-mechanical optical cross-connect with 35.8 Tb/s demonstrated capacity,xe2x80x9d Optical Fiber Communications Conference (OFC 2000), Post deadline paper PD-12, March 2000, or by International Patent Publication WO 00/20899. Moreover, in relation to the micro tilt mirror by the MEMS, there is known the technology disclosed for example in the specification of U.S. Pat. No. 6,044,705.
The basic construction of optical switches using such conventional tilt mirrors, comprises for example, as shown in the perspective view of FIG. 13 and the plan view of FIG. 14, an input collimator array 51A, an output collimator array 51B and two MEMS tilt mirror arrays 52A and 52B. By switching an optical path by changing an angle of input light from the input collimator 51A by the first tilt mirror array 52A, and making the angle of beam return by the second tilt mirror array 52B, the light for which the optical path is switched is incident on the output collimator array 51B.
However, with an optical switch using the conventional tilt mirrors as described above, there has been a problem that high precision is required in mounting the input and output collimators 51A and 51B and the tilt mirror arrays 52A and 52B. As a technique for solving this problem, there is proposed a construction such as that shown in the perspective view of FIG. 15 and the plan view of FIG. 16 where by turning back input light with a mirror 53, and using a collimator array 51 and a tilt mirror array 52 with input sides and output sides formed integrally, respectively, a reduction in the members and adjustment parts is achieved.
However, in an optical switch constructed using a turn-back mirror 53 as shown in the aforementioned FIG. 15 and FIG. 16, because the input section and the output section of the tilt mirror array 52 are arranged on the same plane, then compared to the case of the construction shown in the aforementioned FIG. 13 and FIG. 14, for example when the swing angles of the input tilt mirrors are all set identically, the spatial propagation distance (the optical path length) of the beam in the switch is doubled. Therefore, there is a disadvantage that the optical switch increases in size. In order to reduce the optical path distance, for example, the swing angle of the input tilt mirror may be increased. However, there is a limit to a range of the controllable swing angle of the tilt mirror. Also with a tilt mirror having a large swing angle, since the constructional size becomes large, miniaturization of the overall optical switch is difficult.
The present invention has been achieved in view of the abovementioned points and has an object of providing an optical switch using tilt mirrors, in which easy mounting of optical components is possible by the simplification of construction, and in which a short spatial propagation distance for a light beam is realized.
In order to achieve the abovementioned object, the optical switch using tilt mirrors of the present invention comprises: a collimator array formed with an input section arranged with a plurality of input collimators and an output section arranged with a plurality of output collimators, the input section and the output section being aligned within the same plane; a tilt mirror array formed with an input section arranged with a plurality of input tilt mirrors each of which has a reflection surface with an angle thereof being controllable and an output section arranged with a plurality of output tilt mirrors each of which has a reflection surface with an angle thereof being controllable, the input section and the output section being aligned within the same plane; and a shift type turn-back mirror for shifting an optical path of incident light in a predetermined direction and turning back and outputting this light, wherein the light output from the respective input collimators of the collimator array, is reflected by the corresponding input tilt mirrors of the tilt mirror array so that the optical path is changed, and is then sent to the shift type turn-back mirror, and the light which has been shifted and turned back by the shift type turn-back mirror is reflected by the corresponding output tilt mirrors of the tilt mirror array and then respectively output from the respective output collimators of the collimator array.
With such a construction, after the propagation direction of the light reflected by the input section of the tilt mirror array has been shifted and turned back with the shift type turn-back mirror, the light is sent to the output section of the tilt mirror array. Hence, it is possible to realize a construction where the input and output sections of the collimator array and those of the tilt mirror array are integrated, respectively, without increasing the spatial propagation distance of the light inside the switch. As a result, it is possible to provide an optical switch using small size tilt mirrors with easy mounting for the optical components. Moreover, by reducing the number of optical components, it is also possible to improve stability against disturbances such as temperature fluctuations and vibrations.
Furthermore, for a specific construction of the abovementioned optical switch using tilt mirrors, the tilt mirror array is arranged so that a normal direction of a plane on which the respective reflection surfaces of the input tilt mirrors and the output tilt mirrors are arranged, and a propagation direction of the light output from the input section of the collimator array are not parallel. In particular, preferably the tilt mirror array is arranged so that an angle subtended by the normal direction and the propagation direction of the light from the collimator array is approximately 45xc2x0. By arranging in this manner, it is possible to minimize the distance between the input section and the output section of the tilt mirror array with respect to the swing angles of the respective tilt mirrors.
Further, with the optical switch using tilt mirrors as described above, the arrangement may be such that the direction in which the input section and the output section of the collimator array are aligned, the direction in which the input section and the output section of the tilt mirror array are aligned, and the shift direction of the optical path of the shift type turn-back mirror, are made parallel, respectively, with respect to a reference plane which contains the normal direction for the tilt mirror array and the propagation direction of the light output from the input section of the collimator array. Alternatively, the arrangement may be such that the respective directions are perpendicular to the reference plane. In this case, the spatial propagation distance of the light inside the switch can be made even shorter.
In addition, preferably in the aforementioned optical switch, the respective input tilt mirrors and the respective output tilt mirrors are micro tilt mirrors made applying micro machining technology. By using these micro tilt mirrors, it is possible to even further reduce the size of the optical switch and achieve multichannels.
Moreover, with the optical switch using tilt mirrors as described above, as a specific construction for the shift type turn-back mirror, this may have; a first reflecting surface for reflecting light from the input section of the tilt mirror array to shift the optical path, and a second reflecting surface for reflecting the light from the first reflecting surface to turn this back to the output section of the tilt mirror array. Preferably, an angle subtended by the first reflecting surface and the second reflecting surface is set to approximately 90xc2x0. By setting in this manner, the light beam is turned back in a direction parallel to the propagation direction of the incident light, enabling the design of the optical system to be easily performed.
Other objects, features and advantages of the present invention will become apparent from the following description of embodiments given in conjunction with the appended drawings.